Method of differential coding and modulation

Abstract

A method of coding information for transmission over a communication channel involves differentially coding selected bits of an input sequence with respect to bits of a previous input symbol to generate a transmit sequence comprising a plurality of transmit symbols. The differential coding method can be used in combination with unequal error protection and interleaving to protect bits during transmission.

What is claimed is:  
     
         1 . A method of coding information for transmission over a communication channel, said method comprising: 
 generating a transmit sequence comprising a plurality of transmit symbols based on an input sequence comprising a plurality of input symbols by differentially coding selected bits of said input sequence to produce one or more differentially coded bits in said transmit sequence.    
     
     
         2 . The method of    claim 1    wherein differentially coding selected bits of said input sequence to produce one or more differentially coded bits in said transmit sequence comprises differentially coding one or more bits of a first input symbol with respect to one or more bits from one or more previous input symbols.  
     
     
         3 . The method of    claim 2    wherein differentially coding one or more bits of said first input symbol with respect to one or more bits from one or more previous input symbols comprises differentially coding at least one protected bit of said first input symbol.  
     
     
         4 . The method of    claim 3    wherein differentially coding said at least one protected bit of said first input symbol comprises differentially coding said at least one protected bit of said first input symbol with respect to a less protected bit of a previous transmit symbol.  
     
     
         5 . The method of    claim 2    wherein differentially coding one or more bits of a first input symbol with respect to one or more bits from one or more previous transmit symbols comprises differentially coding at least one unprotected bit of said first input symbol.  
     
     
         6 . The method of    claim 5    wherein differentially coding at least one unprotected bit of said first input symbol comprises differentially coding said unprotected bit of said first input symbol with respect to a protected bit of a previous transmit symbol.  
     
     
         7 . The method of    claim 1    further comprising generating said input sequence based on an information sequence.  
     
     
         8 . The method of    claim 8    wherein generating said input sequence based on said information sequence comprises channel coding bits of said information sequence to produce a coded sequence.  
     
     
         9 . The method of    claim 8    wherein channel coding bits of said information sequence to produce said coded sequence comprises error coding said information sequence using an unequal error protection scheme.  
     
     
         10 . The method of    claim 8    wherein generating said input sequence based on said information sequence further comprises interleaving bits of said coded sequence to produce said input sequence.  
     
     
         11 . The method of    claim 10    wherein interleaving bits of said coded sequence to produce said input sequence comprises diagonally interleaving bits of said coded sequence to produce said input sequence.  
     
     
         12 . The method of    claim 1    further comprising modulating a carrier with said transmit sequence to produce a transmit signal.  
     
     
         13 . A method of decoding a received sequence comprising: 
 differentially decoding a received sequence comprising a plurality of received symbols to generate an output sequence comprising a plurality of output symbols, said received sequence having one or more differentially coded bits.    
     
     
         14 . The method of    claim 13    further comprising demodulating a received signal to generate said received sequence.  
     
     
         15 . The method of    claim 14    wherein demodulating said received signal to generate said received sequence and differentially decoding said received sequence to generate said output sequence are performed jointly in an equalizer.  
     
     
         16 . The method of    claim 13    further comprising channel decoding said output sequence to generate a decoded sequence.  
     
     
         17 . The method of    claim 16    wherein demodulating a received signal to generate said received sequence comprises demodulating said received signal using re-encoded bits fed back from a channel decoder as pilot bits.  
     
     
         18 . The method of    claim 17    further comprising outputting said re-encoded bits from said channel decoder.  
     
     
         19 . The method of    claim 17    further comprising re-encoding said decoded sequence to produce said re-encoded bits.  
     
     
         20 . The method of    claim 13    wherein differentially decoding said received sequence comprising said plurality of received symbols to generate said output sequence comprising said plurality of output symbols comprises differentially decoding one or more bits of a first received symbol with respect to one or more bits from one or more previous received symbols.  
     
     
         21 . The method of    claim 20    wherein differentially decoding one or more bits of said first received symbol with respect to one or more bits from said one or more previous received symbols comprises differentially decoding at least one protected bit of said first received symbol.  
     
     
         22 . The method of    claim 21    wherein differentially decoding said at least one protected bit of said first received symbol comprises differentially decoding said at least one protected bit of said first received symbol with respect to a less protected bit of a previous received symbol.  
     
     
         23 . The method of    claim 20    wherein differentially decoding one or more bits of said first received symbol with respect to one or more bits from said one or more previous received symbols comprises differentially decoding at least one unprotected bit of said first received symbol.  
     
     
         24 . The method of    claim 23    wherein differentially decoding said at least one unprotected bit of said first received symbol comprises differentially decoding said unprotected bit of said first received symbol with respect to a protected bit of a previous received symbol.  
     
     
         25 . An apparatus for coding an input sequence to generate a transmit sequence, said apparatus comprising: 
 a differential coder to generate a transmit sequence comprising a plurality of transmit symbols based on an input sequence comprising a plurality of input symbols by differentially coding selected bits of said input sequence to produce one or more differentially coded bits in said transmit sequence.    
     
     
         26 . The apparatus of    claim 25    wherein said differential coder differentially codes one or more bits of a first input symbol with respect to one or more bits from one or more previous transmit symbols.  
     
     
         27 . The apparatus of    claim 26    wherein said differentially coded bits comprise at least one protected bit.  
     
     
         28 . The apparatus of    claim 27    wherein said at least one protected bit is differentially coded with respect to a less protected bit of a previous transmit symbol.  
     
     
         29 . The apparatus of    claim 26    wherein said differentially coded bits comprises at least one unprotected bit.  
     
     
         30 . The method of    claim 29    wherein said at least one unprotected bit is differentially coded with respect to a protected bit of a previous transmit symbol.  
     
     
         31 . The apparatus of    claim 25    further including a channel coder to channel code an information sequence to generate said input sequence.  
     
     
         32 . The apparatus of    claim 31    wherein said channel coder codes said information sequence using an unequal error protection scheme.  
     
     
         33 . The apparatus of    claim 31    further comprising an interleaver to interleave coded bits output by said channel coder to generate said input sequence.  
     
     
         34 . The apparatus of    claim 33    wherein said interleaver is a diagonal interleaver.  
     
     
         35 . The apparatus of    claim 25    further comprising a modulator following said differential coder to modulate said transmit sequence onto a carrier.  
     
     
         36 . An apparatus for decoding a received sequence comprising: 
 an equalizer to differentially decode a received sequence comprising a plurality of received symbols to generate an output sequence comprising a plurality of output symbols, said received sequence having one or more differentially coded bits.    
     
     
         37 . The apparatus of    claim 36    further comprising a demodulator to demodulate a received signal to generate said received sequence.  
     
     
         38 . The apparatus of    claim 37    wherein said demodulator and said differential decoder are implemented as an equalizer that performs demodulation and differential decoding jointly.  
     
     
         39 . The apparatus of    claim 38    further comprising a channel decoder to decode said output sequence output from said differential decoder to generate a decoded sequence.  
     
     
         40 . The apparatus of    claim 39    wherein said demodulator comprises a multi-pass demodulator that receives re-encoded bits fed back from said channel decoder, wherein said reencoded bits are used as pilot bits by said demodulator to demodulate said received signal.  
     
     
         41 . The apparatus of    claim 36    wherein said differential decoder differentially decodes one or more bits of a first received symbol with respect to one or more bits from previous received symbols.  
     
     
         42 . The apparatus of    claim 41    wherein at least one differentially coded bit comprises a protected bit, and wherein said protected bit is differentially decoded with respect to a less protected bit of a previous received symbol.  
     
     
         43 . The apparatus of    claim 41    wherein at least one differentially coded bit comprises an unprotected bit, and wherein said unprotected bit is differentially decoded with respect to a protected bit.